From cea59022f60f7c9fc6449a31dd4cf4f89ffccf30 Mon Sep 17 00:00:00 2001
From: jamesm <jamesm>
Date: Wed, 2 May 2001 15:45:57 +0000
Subject: Added Fabrice Marie's port of the length match

---
 extensions/.length-test    |   3 +
 extensions/libipt_length.c | 162 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 165 insertions(+)
 create mode 100755 extensions/.length-test
 create mode 100644 extensions/libipt_length.c

diff --git a/extensions/.length-test b/extensions/.length-test
new file mode 100755
index 0000000..52fd62f
--- /dev/null
+++ b/extensions/.length-test
@@ -0,0 +1,3 @@
+#!/bin/sh
+# True if length match patch is applied.
+[ -f $KERNEL_DIR/include/linux/netfilter_ipv4/ipt_length.h ] && echo length
diff --git a/extensions/libipt_length.c b/extensions/libipt_length.c
new file mode 100644
index 0000000..7ea5084
--- /dev/null
+++ b/extensions/libipt_length.c
@@ -0,0 +1,162 @@
+/* Shared library add-on to iptables to add packet length matching support. */
+#include <stdio.h>
+#include <netdb.h>
+#include <string.h>
+#include <stdlib.h>
+#include <getopt.h>
+
+#include <iptables.h>
+#include <linux/netfilter_ipv4/ipt_length.h>
+
+/* Function which prints out usage message. */
+static void
+help(void)
+{
+	printf(
+"length v%s options:\n"
+"[!] --length length[:length]    Match packet length against value or range\n"
+"                                of values (inclusive)\n",
+NETFILTER_VERSION);
+
+}
+  
+static struct option opts[] = {
+	{ "length", 1, 0, '1' },
+	{0}
+};
+
+/* Initialize the match. */
+static void
+init(struct ipt_entry_match *m, unsigned int *nfcache)
+{
+	*nfcache |= NFC_UNKNOWN;
+}
+
+static u_int16_t
+parse_length(const char *s)
+{
+	int len;
+	
+	len = string_to_number(s, 0, 0xFFFF);
+	
+	if (len == -1)
+		exit_error(PARAMETER_PROBLEM, "length invalid: `%s'\n", s);
+	else
+		return (u_int16_t )len;
+}
+
+/* If a single value is provided, min and max are both set to the value */
+static void
+parse_lengths(const char *s, struct ipt_length_info *info)
+{
+	char *buffer;
+	char *cp;
+
+	buffer = strdup(s);
+	if ((cp = strchr(buffer, ':')) == NULL)
+		info->min = info->max = parse_length(buffer);
+	else {
+		*cp = '\0';
+		cp++;
+
+		info->min = buffer[0] ? parse_length(buffer) : 0;
+		info->max = cp[0] ? parse_length(cp) : 0xFFFF;
+	}
+	free(buffer);
+	
+	if (info->min > info->max)
+		exit_error(PARAMETER_PROBLEM,
+		           "length min. range value `%u' greater than max. "
+		           "range value `%u'", info->min, info->max);
+	
+}
+
+/* Function which parses command options; returns true if it
+   ate an option */
+static int
+parse(int c, char **argv, int invert, unsigned int *flags,
+      const struct ipt_entry *entry,
+      unsigned int *nfcache,
+      struct ipt_entry_match **match)
+{
+	struct ipt_length_info *info = (struct ipt_length_info *)(*match)->data;
+
+	switch (c) {
+		case '1':
+			if (*flags)
+				exit_error(PARAMETER_PROBLEM,
+				           "length: `--length' may only be "
+				           "specified once");
+			if (check_inverse(optarg, &invert))
+				optind++;
+			parse_lengths(argv[optind-1], info);
+			if (invert)
+				info->invert = 1;
+			*flags = 1;
+			break;
+			
+		default:
+			return 0;
+	}
+	return 1;
+}
+
+/* Final check; must have specified --length. */
+static void
+final_check(unsigned int flags)
+{
+	if (!flags)
+		exit_error(PARAMETER_PROBLEM,
+			   "length: You must specify `--length'");
+}
+
+/* Common match printing code. */
+static void
+print_length(struct ipt_length_info *info)
+{
+	if (info->invert)
+		fputc('!', stdout);
+	
+	if (info->max == info->min)
+		printf("%u ", info->min);
+	else
+		printf("%u:%u ", info->min, info->max);
+}
+
+/* Prints out the matchinfo. */
+static void
+print(const struct ipt_ip *ip,
+      const struct ipt_entry_match *match,
+      int numeric)
+{
+	printf("length ");
+	print_length((struct ipt_length_info *)match->data);
+}
+
+/* Saves the union ipt_matchinfo in parsable form to stdout. */
+static void
+save(const struct ipt_ip *ip, const struct ipt_entry_match *match)
+{
+	printf("--length ");
+	print_length((struct ipt_length_info *)match->data);
+}
+
+struct iptables_match length
+= { NULL,
+    "length",
+    NETFILTER_VERSION,
+    IPT_ALIGN(sizeof(struct ipt_length_info)),
+    IPT_ALIGN(sizeof(struct ipt_length_info)),
+    &help,
+    &init,
+    &parse,
+    &final_check,
+    &print,
+    &save,
+    opts
+};
+
+void _init(void)
+{
+	register_match(&length);
+}
-- 
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